A fuel carrying member such as an internal manifold of a gas turbine engine must survive inside a hot environment while protecting the fuel flowing therein from being subjected to high temperatures. To accomplish this, a heat shield is used around the internal manifold to minimize convective heat transfer thereto. The heat shield is exposed to much higher temperatures than the internal manifold and acts to insulate the latter. As heat transfer still occurs to a certain degree, the internal manifold further relies on high velocity fuel flow to act like a heat sink to reduce the temperature of the metal.
Thus, fuel coking under steady state conditions becomes a major concern as the fuel flow experiences a temperature rise while traveling through the internal manifold. Furthermore, the fuel is gradually depleted as it travels from the inlet through the internal manifold feeding each nozzle in its path. As the volume and the velocity of the fuel decreases, the heat input into the internal manifold becomes more problematic. This is particularly true at the point furthest away the inlet of the internal manifold where there is generally no fuel flow but a constant heat input. Without or with very little fuel flow to act as a heat sink, the internal manifold may heat in these susceptible areas to temperatures above fuel-coking threshold levels. Therefore, there is a need to reduce the temperature of the internal manifold at locations susceptible to overheating so as to mitigate the risk of fuel coking.
Accordingly, improvement in the internal manifold assembly design is sought.